Method of producing propeller blades



J. SQUIRES 2,081,645

METHOD OF PRODUCING PROPELLER BLADES May 25, 1937.

'7 Sheets-Sheet 1 Filed July 5, 1953 INVENT OR JO]! 7 60 Va res.

BY I

ATTORNEYS- y 1937- J. SQUIRES 2,081,645 METHOD OF PRODUCING PROPEL LER BLADES Filed July s, 1933 7 Sheets-Sheet 2 INVENTOR J'o I??? 5 Q (fire 5.

May 25, 1937. SQUIRES 2,081,645

METHOD OF PRODUCING PROPELLER BLADES Filed July 5, 1933 7 Sheets-Sheet 3 I /J&

a {/70 r E B- we 7 /az M6 INVENTQR J0 SQZ/L'rcS.

TORNEY .May 25, 1937.

J. SQUIRES METHOD OF PRODUCINGVPROPELLER BLADES Filed July 5, 1933 7 Sheets-Sheet 4 INVENTOR J07 SQZ/ir'cs.

ATTORNEYS.

I/{IIIIIIII May 25, 1937. .1. SQUIRES METHOD OF PRODUCING PROPELLER BLADES Filed Jul 5, 1935 7 Sheets-Sheet 5 INVENTOR J'bivr 5 1/L'f65.

May 25, 1937. J. SQUIRES METHOD OF PRODUCING PROPELLER BLADES 7 Sheets-Sheet '7 Filed July 5, 1955 INVENTOR BY) I I of RNEYS.

Patented May 25, 1937 PATENT OFFICE METHOD OF PRODUCING PROPELLER BLADES John Squires, Hagerstown, Md., assignor to United Aircraft Corporation, East Hartford,

Conn., a, corporation of Delaware Application July, 5, 1933, Serial No. 679,13

'78 Claims.

This invention relates to airplane propellers and particularly to the blades thereof, the principal object being the provision of a blade for such propellers together with improved methods.

of the tube is then swaged or otherwise tapered to a somewhat smaller diameter both internally and externally. The blank is then held by the flange while there is inserted into it a mandrel under sufiicient pressure to bring the internal dimensions of the tube to approximately the size of the mandrel. After the mandrel is withdrawn the inner face of the smaller end of the tube is dressed to substantially the size desired in the finished tube. The tube is again held by the flange and the mandrel inserted into it the tip end seating upon the dressed portion at the smaller end of the tube. The mandrel is then forced home under pressure causing the main body portion of the tube to expand, contract or deform beyond its elastic limit. This will cause the tube to permanently assume an interior size substantially exactly corresponding to the external dimensions of the mandrel which is of the size desired for the further operations on the tube. The sized tube upon a correspondingly sized mandrel is then placed in a lathe where the surface of the tube is acted upon in such a way as to cause the wall of the tube to very closely approach the thickness desired n the finishedproduct. Preferably the wall will be somewhat tapered in thickness being thinner at the smaller end of the tube. A mandrel or support is then placed in the tube engaging it near the smaller open end. While so carried, in a turning lathe, the metal at the smaller end of the tube is heated and as it becomes plastic it is worked upon by a spinning tool or the like to entirely close the tube at the smaller end at the same time slightly thickening the metal and forming a small nipple thereon. The blank is then freely revolved on horizontal supports to ascertain its heaviest portion if any. The closed tube is then preferably suspended by the flange in a heating furnace and brought to'a proper temperature for the final forming operation. The forming operation is performed by placing the heated blank, properly positioned with respect to its heavy line, between tudinal axis of the blade.

a pair of dies where it is held by its flange. Air under pressure is admitted to the interior of the tube and the dies are caused to come together and press the tube in proper form for an airplane propeller. The shaped tube may then be again suspended by its flange in a furnace and heated to relieve strains in the metal after which it may again be inserted in the dies which may be suitably cooled to chill the metal and cause the propeller to set in its flnal form. For convenience the dies may be madein separate sections so that they may be partially or wholly changed to produce blades of difierent characteristics. The die cavity toward the tip or smaller end of the blade may be of somewhat larger capacity than the finished blade. The means for supporting the blade by its flange for the pressing and finishing operation may be resiliently mounted so as to conveniently provide for contraction of the metal when cooling. The propeller blade when taken from the dies may have the nipple formed at its tip removed and a small hole drilled in its camber face near the tip. The flange may now be dressed or cleaned up and the blade suspended from a centering spider mounted in the flange end of the tube over a marker for marking on the tip the other end of the longi- The blade may then be mounted by its flange in a balancing stand and appropriately corrected to bring its static moment into correspondence with a predetermined standard. This may be done by cutting or dressing the flange in accordance with the need indicated by the balancing mechanism. Suitable polishing, finishing, heating, straightening and correcting operations may take place at suitable points during the operation. It will be understood the description here given is a general outline of what has been found workable, further details of which m'll appear hereinaiter. All of the matter here stated is not essentialto all phases of the invention and may not all be necessary with respect to anyindividual propeller.

Objects of the invention include the provision of a propeller blade formed from standard tubular stock through subjecting the same to suitable forming operations; to provide for gradually reducing the thickness of the walls of a hollow propeller blade or blade blank from its inner to its outer end, so as to vary the strength ofthe blade at difierent points of itslength, according to stresses encounteredat such points-in use, and thus greatly reduce the magnitude oi; cen--" trifugal stresses arising in such iise. 5

Other objects include certain steps of operation in the method of forming a propeller blade among which are included the formation of a hollow blank having one end thereof of smaller dimensions than the opposite end thereof, and accurately predetermining the interior size, shape and contour of such blank prior to bringing such blank to blade formation; to accurately predetermine the interior dimensions of such blank and thereafter machine the exterior of such blank in predetermined accordance with the internal dimensions thereof; to predetermine such internal dimensions of the blank by a radial stretching of the blank beyond the elastic limit of its material; to predetermine such internal dimensions of the blank by axial stretching of the blank beyond the elastic limit of its material; to predetermine such internal dimensions of the blank by radially and axially stretching of the blank beyond the elastic limit of its material; to accurately predetermine the internal dimensions of such blank at least in part by forcing into the blank a mandrel of predetermined shape, size and contour with sufficient force to stretch the material of the blank, or at least a portion thereof, beyond the elastic limits of the material of which it is formed; to accurately predetermine the interior size, shape and contour of at least a portion of said blank by forcing into it a mandrel which will cause such portion to be stretched both axially and radially to thereby cause the interior walls of said portion to set and to conform permanently to the complementary surface of the mandrel.

Other objects of the invention reside in the method of forming a propeller blade which includes the machining .of the interior surface of the smaller end portion of the blade blank prior to accurately predetermining the interior size, shape and contour of the remaining interior dimensions of the blank; machining the interior surfaces of the smaller end. of the blank and thereafter forcing into the blank a mandrel of predetermined size, shape and contour whereby to stretch the metal beyond its elastic limit, to cause the interior surfaces of the blank to conform to the external surfaces of the mandrel; to accurately predetermine the interior size, shape and contour of at least a portion of the smaller end of the blank by a machining operation and thereafter causing the remaining interior walls of the blank to conform to a predeterminedsize, shape and contour by stretching the blank'beyond the elastic limit of its metal over a mandrel.

of predetermined size, shape and contour.

Other objects of the invention reside in the method of forming a propeller blade blank including closing the small end of the blank; closing the small end of the blank in such 'a manner as to provide an extra thickness of metal at such end; closing such small end of the blank by a succession of passes of a spinning tool; closing such small end of the blank by workingthe metal of such end over the end surface of a mandrel mounted within the blank; closing such small end of the blank by Working the metal of such end over a mandrel received therein so as to cause the interior size, shape and contour of such end to conform to the external size, shape and contour of such mandrel; and to close such end by working the metal thereof over the corresponding end of a mandrel in such a manner as to cause a nib or nipple to be formed at the tip of such end by flowing excess metal in the end toward the tip thereof.

Other objects include predetermining the interior size, shape and contour of a propeller blade blank and then machining the exterior of the blade in predetermined relationship with respect to the interior surface thereof; accurately predetermining the interior size, shape and contour of a blank, placing said blank upon a mandrel whose exterior surface accurately conforms to the interior surface of the blank, and then machining the exterior surface of the blank in predetermined relationship to the exterior surface of the mandrel.

Other objects include the provision of a method of making a propeller blade blank including operating upon a length of tubular stock to form a flange at one end thereof and to bring the other end to smaller dimensions; operating upon such length of stock to bring its internal dimensions into conformance to a predetermined size,

shape and contour, operating upon the exterior of said stock to bring the wall thickness thereof to that desired in the finished product and then operating upon said blank so formed to bring it to the desired blade shape; operating upon a tubular piece of metal to bring it into generally tapered conformation with the ends thereof open, machining the tube thus tapered to bring its wall thickness to desired finished condition, closing the small end of the tube and thereafter pressing the tube to the desired blade shape; and to providea method of forming a blade as outlined above in which the surface of the tube is polished before the tube is pressed to blade formation.

Other objects include improvements in the method of making propeller blades including certain steps of operation designed to result in a product of material uniformity in quality; to provide a method including certain steps of operation in the formation of a blank for propeller blades, in certain steps of operation in modifying the blank into blade formation,. and in certain steps in and methods of heat treatment of the blank after it has been formed to shape.

Other objects of the invention are to obviate both statically and dynamically unbalanced conditions in propellers of the type used on airplanes; to provide animproved balancing method for this purpose by which corrections may be individually made in each blade of the propeller;

and to provide a method of this kind permitting i rendering identical the moment characteristics of propeller blades with respect to a corresponding reference plane of each so that one or both blades of a propeller may be removed and replaced without requiring the assembled propeller Other objects include the provision of a protion, and illustrate successive steps'of machining form a flange without distorting the flow lines of the metal from which the flange is formed.

Other objects include the provision of a method and means for'accurately locating the center of mass of a propeller blade on the longitudinal axis of the blade"; and the provision of a method of accurately forming the portion of a propeller blade to be received in the hub of a propeller blade in accurate conformance with the axial line of the blade. I

Further objectsinclude a method of obtaining a predetermined condition of balance of a hollow metallic propeller blade by applying material to 1 the interior surface thereof; the method of obraining such balance by applying a paint-like or similar material to an interior surface thereof;

, and the method of obtaining such balance by applylngsuch material to the interior of. the blade through an opening in a wall of the blade;

- The above being among the objects of the present invention, the same consists in certain novel features of construction of a propeller blade and/era blank therefor, and apparatus for producing and/or testing such blade and/or blank, and methods and/or processes and/or steps of methods and/or processes'capable of use during one or more-of the phases of operation involved in the production of such blade and blank, as above pointed out, or as will be more specifically brought out in connection with the following description, reference being had to the accompanying drawings forming a part thereof.

In the accompanying drawings which illustrate suitable embodiments of the invention herein involved, and'in which like-numerals refer to like parts throughout the several different views,

Figure 1 is a side elevational view of a com pleted propeller blade of a type with which the present invention deals.

Fig. 2 is a transverse sectional view taken through the body of the propeller blade shown in Fig. 1 as on the line 2-2 of Fig. 1. Fig. 3 is a side elevation, and Fig. 4 is an end elevation, of a tube of the type'which preferably forms the initial piece 'of stock from which the airplane propeller of the present invention is finally formed.

Figs. 5 to 13 inclusiveare partially broken, par: tially sectioned, side elevational views, Figs. 11 to -13' being enlarged, which illustrate successive steps of operation-upon one end of the piece of stock shown in Figs. 3 and 4 during the formation of a flange thereon which, after subsequent operations, will serve as means for supporting the propeller blade in a hub structure.

Fig. 14 is a side elevational view of the piece of stock shown in Figs. 3 and 4 after it has been subjected to the operation illustrated in Figs. 5 to 13 inclusive whereby a flange is formed upon one end thereof, and after it has been tapered and reduced in. diameter especially at the opposite end to form a small end.

Fig. 15 'is an enlarged fragmentary vertical sectional view taken axially through the small end of the piece of stock or blank shown in Fig. 14 and illustrating how the wall thickness of such end is increased during the operation of forming thesmallend.

Fig. 16 is a more-or-less diagrammatic sectional view taken along the axis of the blank shown in Figs. 14 and 15. and illustrating the method and apparatus preferably employed for initially sizing the interior of the blank.

Figs. 17 and 18 show the blank resulting from the operation indicated in Fig. 16, in axial secthe interior surfaces of .thesmall end portion thereof. i

Fig. 19-is a view similar to Fig. 16 and illustrates the final step of operation in and apparatus for bringing'the. interior size, shape and contour of the blank into conformance with a predetermined standard. C I

Fig. 20 shows the blank resulting from the operation indicated in Fig. 19, in axial section, and mounted upon a mandrel for the purpose of testing the accuracy of its internal dimensions.

Fig.21 is a more-or-less diagrammatic frag- .mentary plan view, illustrating the blank indicated in Fig. 20 mounted upon a mandrel in a lathe and in the process of having its exterior surface machined. I

Fig. 22 is a transverse sectional view taken on the line 22-22 of Fig. 21.

- Fig. 23 is an enlarged fragmentary sectional view'of the small end of the blank after it comes from the lathe indicated in. Figs. 21 and 22, and illustrating. the apparatus employed for closing the small and of the blank and before such apparatus has acted upon the blank.

Fig. 24 is a view similar to Fig. 23 but illustrating additional apparatus employedin the closing of the small end of the blank and illustrating the small end of the blank after one of the initial closingoperations thereon.

' possible heavy-side thereof.

Fig. 28 is an enlal'ged transverse sectional view taken on the line 28-28 of Fig. 2'7.

Fig. -.29, is a m'ore-or-lessdiagrammatic reduced vertical, sectional view taken centrally through a furnace in which the blank in the form illustrated in Figs. 27 and 28 is shown positioned, and whichfurnace may be employed for heating the blank to condition it. for subsequent pressing operation and/or for heat treating the blank.

Fig. 30 is a fragmentary perspective view of an improved forming apparatus preferably employed for pressing the blank indicated in Fig. 2.9 to blade shape, showing parts thereof removed to disclose the underlying structure.

Fig. 31 is a horizontal sectional view taken centrally through the forming apparatus as on the line 3|-3I of Fig. 32, showing the dies thereof in' closed position and illustrating the manner in which the blank is mounted and internally supported.

Fig. 32 is a vertical sectional view taken on the line 3232 of Fig. 3.1. V v Fig. 33 is a fragmentary partially broken top plan view of the apparatus illustrated in Figx31, a portion of the upper wall'having been removed to disclosethe cooling medium passages therein.

'Fig. 341$ a front end view of the forming apparatus showing the die holders anddles in their adjacent closed position.

Fig. 35 is a transverse vertical sectional view taken on the line 35-45 of Fig. 31.

Fig. 36 is a front end view, similar to Fig. 34,

Fig. 38 is afragmentary perspective view of a quenching apparatus into which the forming apparatusabove disclosed may be conveniently converted by the addition of accessory equipment and showing a further development of this phase of my invention. r

Fig. 39 is a front end elevation of thestructure in Fig. 38. v

Fig. 40 isa fragmentary longitudinal sectional view taken vertically through the center of the structure shown in Figs. 38 and 39, as on the line 40-40 of Fig. 39.

Fig. 41 is a fragmentary enlarged side eleva'-- tional view of the tip of the propeller blade show- Fig. 42 is a fragmentary side elevational view of the shank end of the blade illustrating an initial 'machining operation upon the. flange thereof.

Fig. 43.is a side elevational view of theipropeller blade. illustrating the procedure preferably employed in determining the center line or axis of the blade which i mass of the blade.

Fig. 44 is a side elevational view of the apparatus preferably employedfor determining the final location of the flange at the root of the blade with respect to the center of mass of the blade, a fragment of .a propeller blade being shown 1 mounted therein.

Fig. 45 is a sectional view taken on the line ira-450i Fig. 44.

Fig. 46 is a-plan view of the apparatus shown inFig.44.', v

Fig. 4'7 is a side elevational view of the apparatus of Fig. 44 in a vertical position.

Figs. 4a, 49 and 50 illustrate the positions atwhich metal may be'removed from the flange of v the blade, shown enlarged, in order to bring the final position of the flange into predetermined accordance with respect to the center of 'mass of' the blade as determined by the apparatus illustrated in Figs. 44 to 47, inclusive.

It will be understood that in the following blade from material other than steel, those skilled specification and its reference to the accompany ing drawings, a plurality of steps or series of steps of operation have been shown and disclosed which have been found, when combined with each other, to result in certain economies in production and desired accuracy and quality in the resultant blade produced. However, it is not to be :understood that the invention, in its broader of any other step or series of steps of operation that may lead up to or may follow such particular step or seriesof steps of operation. Accordingly, it will be understood that wherever,

in the following specification, a particular step or series of steps of operation is capable of being employed independently of any other steps or series of stepsof operation, such step or series of steps of operation is, in and of itself, to be considered a complete invention, separate and ing the drainage or vent openinglprovided'thereat the opposite end thereof.

cordance with the broader aspects of the present s to pass through the center of and described consisting as a whole of various parts or elements. While :the features shown combine to make a desirable propeller, the invention is not confined to all details shown as combined, but the various features or phases of the propeller blade may comprise inventions and may be used alone or in other connections or without all the other -features or phases illustrated.

. Referring. now to Figs. 1 and 2 of the drawings, a propeller blade of the type particularly adaptable to the practices of the present invention, is shown. 'This propeller blade is of hollow construction, and preferably formed of steel, and includes a main body portion I having a tip I02 at one end thereof and a shank portion I04 Although, in acinvention, the particularmeans provided in connection with the shank'portion iM for aiding in securing the propeller blade in a hub structure not shown) is more or less immaterial, a preferred form of such means is shown in Fig. 1 in the form of a single outwardly extending annular flange I at the root end of the shank portion HM. It will also be understood that the main body portion I00 of the propeller blade is generally of airfoil section, and provided with a leading edge wand a trailing edge lifl and has a front or camber'face 0a and a rear or flat face H01), and that preferably the main body portion 800 is more or less twisted or warped over its length in order that each increment of the length thereof has substantially the same pitch as any othersuchincrement. Thehollowtypeof propeller I blade is preferred generally for the reason that when properly constructed, it providesv maximum strength for agiven weight. -While all phases of the invention areiiot confined thereto, the following description will deal solely with the preferred form and manner of making the propeller blade shown in Figs. 1 and 2. It may also be noted that although the propeller blade shown in Figs. 1 and 2 may be constructed of material other than steel, the following description will deal solely with the construction of such blade made from steel, and should it be desired to form such a steel tube of suitable length and of an external and internal diameter slightly larger and smaller than the respective external and internal diameters of the finished blade respectively at a point adjacent the outer end of 'the shank portion I04.

Of course, in thebroader aspects of the invention, 1

the particular composition of the steel employed may vary in accordance with the desire of the particular designer or manufacturer, but for the purpose or illustration in the present case, will be considered to be of that type known as 4130-2, the composition of which is well known to those in the industry and is disclosed, as for' instance, in the S. A. E. Handbook published by Society of Automotive Engineers, Inc., 29 West 39th Street, New York, New York. Another composition of steel disclosed in said S. :A. E. Handbook and known as 6135 is also suitable for the.

blank I I2, as are many others there disclosed.

Preferably, the first operations upon the blank H2 are in connection with the formation of the shank I04 and flange I06, as disclosed in Figs. 5 to 13, inclusive. The first of these operations, as indicated in Fig. 5,' include placing one end of the blank H2 in a die structure, indicated generally at H4. This die structure is provided with an opening H6 therein, which relatively closely embraces the circumference of the blank H2 at one end of the die structure and beyond such end of the die structure the opening is enlarged in diameter in concentric relation with respect to the opening H6, as at H8, this portion being joined to the opening H6 through a tapered shoulder portion I20. In positioning the blank H2 in the die structure H4, as illustrated in Fig. 5, the left hand end of the blank H2 is. preferably located slightly inwardly or to the right from the left hand face of the die structure, and the blank I I2 is suitably anchored against movement to the right, as indicated in Fig. 5. As indicated in Fig. 5, there is employed a ram I22 of a diameter to be freely received within the enentered into the bore of the blank H2 and the body of the ram I22 is entered into the opening I I8 a sufficient distance to bring the shoulder I26 into contact with the corresponding end of the stock H2 and sufficient pressure is exerted upon the ram I22 to cause the corresponding end of the blank I I2 to be upset and thereby cause it to conform externally to the walls of the opening II 8 and of the shoulder I20, and internally to conform to the diameter of the pilot I24. This operation forms an enlarged cylindrical portion I06a which eventually will provide the flange I05, and an outwardly tapered portion I04a which when brought to completed form will provide part of the shank portion I04. This end of the blank is, of. course, preferably previously brought to a forging temperature, approximately 2200 F. in the case of the particular steel disclosed, for the purpose of subjecting it to this step of operation.

Upon completion of this operation, the blank H2 is removed from the die structure, and the upset end thereof is again brought to forging temperature and again placed in a die structure similar to the die structure I I4, to be again acted upon by a ram similar to the ram I22. The only difference is that in this case the opening in the die structure which corresponds to the opening H8 in Fig. 5 is of greater diameter than the opening H8, while the opening in the die structure corresponding to the opening H6 in Fig. 5

is the same as in Fig. 5, and accordingly the.

length of the shoulder in the die structure corresponding to the shoulder I20 in Fig. 5, is correspondingly increased. The diameter of the ram in this case, corresponding to the ram I22, is. of course increased in accordance with' the increase in diameter of the opening in which it is to be received, and the diameter of the pilot corresponding to the pilot I 24 in Fig. 5 is slightly reduced over the diameter of the pilot I24. With the modified die structure and ram the upset end of the blank H2 is again acted upon in substantially the same manner as described in connection with Fig. 5, the result being substantially as indicated in Fig. 6, that is, the external diameter of the portion I06a is increased, and the internal diameter is decreased over that indicated in Fig. 5, and the length of the tapered shoulder I04a is increased, while the length of the end operated on is somewhat decreased.

The upset end of the blank H2 may be then again heated to forging temperature and may be again subjected to the action of apparatus similar to that disclosed in Fig. 5 to further increase the diameter of the portion I06a and the length of the shoulder mm and decrease the internal diameter of the blank over the length of these portions so as to bring this end of the blank into substantially the form indicated in Fig. 7. This end of the blank H2 is subjected to as many repetitions of this type of operation as is deemed necessary to bring this end of the blank into approximately the condition indicated in Fig. 8, having proper regard to the grain structure and flow lines of the grain of the metal in such end. For this latter reason it will be apparent that, although the end of the blank as indicated in Fig. 3 could be brought to the condition illustrated in Fig. 8 in a single operation instead of a plurality of operations as disclosed, the grain structure of the metal in such case might be adversely affected and the flow lines of the grain of the metal might be unduly distorted from the viewpoint of obtaining maximum strength in this portion of the final product. By following out a suitable number of operations as described, it is possible to maintain substantially the same grain structure and grain flow lines as occur in the original piece of stock or blank H2.

When the blank I I2 reaches the form indicated in Fig. 8, the tapered shoulder portion I04a has assumed substantially the form and size of the shank portion I04 in the finished blade, its size of course being slightly larger for the purpose "of leaving sufiicient stock thereon to clean it up in subsequent machining operations. .The thickness of the portion I06a at this stage of operation is substantially greater than'the thickness of the flange I06 in the final product. The internal diameter of the blank over the length of the portions I06a and I04, as indicated in Fig. 8, has

been reduced sufiiciently so that upon removing the excess metal from the interior of the blank at this point to bring it into conformance with the diameter of the main body portion of the blank, any roughness or other imperfections which may have appeared on the interior of the blank at this point during the upsetting operation will be fully removed.

It will be understood that the exact sizes or proportions indicated in the drawings are not essential and that the deformation of the end of the blank H2 and at other points in the operation may be carried out to whatever extent is desired or expedient to produce the desired propeller blade or. blank.

The next steps of operation deal with the outward bending of the portion I06a so as to form a blank, as indicated in Fig. 11 from which the flange I06 may be formed. These steps of operation include preferably three or more steps as indicated in Figs. 9, 10 and 11 in which the portion J06 of the blank, as indicated in Fig. 8, is gradually bent outwardly with respect to the axis of the blank until the metal of such portion is brought into a plane perpendicular to the axis of the blank as indicated in Fig. 11. These operations are preferably not of an upsetting character but consist rather of an outwardly bending or belling of the portion IIlIia so as not to disturb the grain structure or grain flow lines of this portion and, of course, are preferably conducted while this portion of the blank is at about forging temperature. The operation may be performed in any suitable number of steps. The final step of operation in bringing this end of the blank to the form indicated in Fig. 11 may, if necessary, include a certain amount of forming, as distinguished from pure bending or belling, in order to obtain the desired contour of this end. The entire procedure may be effected by any desired suitable known means which are not shown.

The next operation, which is illustrated in Fig. 12, consists in mounting the blank H2 in a lathe or other suitable structure in which the blank may be accurately centered and by means of a tool such as I28, turning the periphery of the flange portion I06 into a cylindrical form concentric with the axis of the blank I I2.

This end of the blank H2 is then accurately centered, as by means of a stead rest I30, in a lathe or other structure and the excess metal in the bore formed during the upsetting process disclosed in Figs. 5 to 8, inclusive, is then removed, as by means of a tool such at I32 where the amount of metal to be removed is relatively large, or by other suitable means, so as to bring this portion of the bore into accurate conformance with the initial bore of the blank, and then this portion is ground, bufied or otherwise acted upon to bring the internal surface thereof into smooth, polished and unbroken relation with respect to the bore of the main body portion thereof. The manner of forming the flange described in connection with Figs. 5 to 13, inclusive, has been found to be a practical way of providing a flange on the tube, but the decreasing of the internal dimensions of the blank during the flange forming operation and subsequent removal of the excess metal of the bore at this end of the blank is not my invention and may be eliminated if desired or other suitable flange forming operations may be adopted in the place of that described. The above described method of flanging the blank forms the subject matter of my application for Letters Patent of the United States for Improvements in method of flanging metal tubes, filed January 2'7, 1937, Serial No. 122,631, the same constituting a division of the present application.

The next step of operation is in connection with inwardly tapering especially the end of the blank II2 opposite the flange I06 to form a small, nose or tip portion I34 as indicated in Fig. 14. This operation upon the blank may be conducted by one or more suitable swaging or other operations well known to those skilled in the art, and while the operation may be a cold swaging operation in whole or in part, particularly in the final stages, the blank or such end of the blank is preferably repeatedly brought to a forging temperature so as to maintain the plasticity of the metal during the operation and maintain the proper grain structure and grain flow lines of the metal. One commercial way to produce this taper is by the use of clapper dies, using several dies and gradually getting the tapered shape in several passes in the dies. noticeable toward the small or. nose end of the blank it may be tapered slightly throughout substantially its entire length. In addition, it is While the taper is especially preferable to normalize and pickle the blank before beginning these operations, and, if necessary, one or more times during the tapering process. Also, before the final tapering operations on the nose portion I34, it is preferable to normalize, pickle and straighten the blank. The normalizing treatment in the case of the particular steel specified as by way of example may be to raise the temperature of the blank to 1625-1675 degrees F. in a suitable furnace, holding the temperature at this value for approximately twenty minutes, and then shutting off the heat and let ting the blank cool in the furnace until its temperature falls below 1200 degrees F. when it may be removed to cool in the air or for further operations about to be described.

As will be apparent to those skilled in the art, such operation upon the end of the blank H2 to form the nose portion I34 may result in a thickening of the wall of the blank of this portion in somewhat the manner indicated in Fig. 15. Such operation upon the end of the blank to form the nose portion I34, due to the crowding in of the metal thereof, may cause folds, wrinkles or other imperfections to develop upon the inner surface of the nose portion I34 of the blank I I2.

After the above described operation the internal shape, size and contour of the blank H2 is approximately but of slightly smaller dimensions than that desired in the completed blank immediately prior to pressing it to blade formation, and the following steps of operation upon the blank are preferably those dealing with the bringing of the internal size, shape and contour of the blank into exact conformance with that desired in the completed blank, and the preferred method of accomplishing this result will now be explained in detail.

The bed I36 of a suitable power press or bull dozer is provided with an opening I38 therein. One end of the opening I38 is enlarged as at I40 in order to receive the die insert I42 therein. The die insert I42 is provided with a central opening concentric with the opening I38 and formed complementary to the tapered shoulder I04 of the blank H2 and the blank H2 is inserted therein in the manner illustrated in Fig. 16 with the face of the flange I06 resting against the face of the insert I42 so as to take the force of the stretching operation. The ram I44 of the power press has secured thereto a mandrel I46, the size, shape an contour of which conforms exactly to the predetermined internal size, shape and contour of the desired finished blank and which, accordingly, is slightly larger than the interior size, shape and contour of the blank I I2 in the condition in which it is represented in Fig. 14. The mandrel I46 is preferably tapered over the main body portion thereof a slight amount to give greater ease in inserting and removing it from the blank. A ring or spacing washer I48 ispreferably placed about the mandrel I46 and against the shoulder formed at the junction between the mandrel I46 and ram I44 for the purpose of relieving this shoulder of any wear that might otherwise occur in subsequent operations and for accurately controlling the amount of penetration of the mandrel into the blank. In addition, for use in connection with the first operation of the mandrel I46 upon the blank I I2, a supplementary ring or spacing washer I50 is employed in conjunction with the ring I48. The length of the mandrel I46 is preferably such that when the ring I48 contacts with the surface of the flange I06, the mandrel I45 will have been forced fully home in the blank I I2.

Consequently, in the initial operation of the mandrel I46 upon the blank II2, the ring I56, which for blank forming blades of usual sizes is preferably in the neighborhood of one-half of an inch thick, will permit the mandrel to be forced into the blank only to within this distance of its final position.

Before any attempt is made to force the mandrel I4'6 into the blank II2 by the power press, the exterior of the mandrel I46 is preferably coated with white lead and graphite or other suitable lubricant, and then the mandrel I46 is forced into the blank I I2 to the position indicated in Fig. 16. In forcing the mandrel I46 into the blank II2 as illustrated in Fig. 16 which opera- .tion is conducted while the blank H2 is cold. that is, not artificially heated, the mandrel causes the blank to be stretched until its internal size, shape and contour is forced to conform to the external size, shape and contour of the mandrel, and ordinarily this causes the blank to be stretched both radially and axially. It may be noted that, because of the reduced dimensions of the nose portion I34 of the blank and because of the increased wall thickness of this portion produced during the nose forming operation, ordinarily very little stretching of the nose portion I34 will be caused by the mandrel I46 and con-= sequently when once the nose portion of the mandrel I46 contacts with the nose portion I36 of the blank, further inward movement of the mandrel I46 will tend to stretch the-blank longitudinally or axially. Under such circumstances should, for any reason, any portion of the interior wall surface of the body portion of the blank IIZ be not in firm contact with the outer surface of the mandrel I46, the subsequent axially stretching of the blank II2 as the mandrel I46 is forced in will tend to cause a radial contraction of the blank which, in most cases, will bring substantially all portions of the interior wall into contact with the surface of the mandrel, and consequently remedy this undesired condition. It may also be noted that inasmuch as this operation is designed to initially and permanently size the interior of the blank, the material of the blank must ordinarily be stretched beyond its elastic limit by the movement of the mandrel so that the effect of such stretching will be permanent.

The next operations are concerned'with bringing the interior size, shape and contour of the nose portion I34 of the blank I I2 into accurate conformance with a predetermined standard. It has been explained above that ordinarily this is impractical by the use of the mandrel I46 alone for the reason that the nose portion I34 is of reduced diameter and of increased wall thickness, but it will be apparent that in any case the mandrel I46 would not in all cases remove any folds or wrinkles on the interior surface of the nose portion I34 that may have appeared during the nose forming operation referred to in connection with Fig. 14. Consequently, in order to be absolutely sure that no folds, wrinkles or other defects remain and that theinterior size,shape and contour of the nose portion I34 will accurately conform to a predetermined standard, it is subjected to one or more reaming operations in which metal is actually removed from the interior surface of the nose portion I34.

Such removal of metal from the interior surface of the nose portion I34 is conveniently accomplished by the employment of formed reamers such as the reamer I52 illustrated in Fig. 17 and the reamer I54 illustrated in Fig. 18, the reamer I52being illustrated as a roughing reamer and the reamer I54 being illustrated as a finishing reamer, but it will be apparent that as many reamers'of this type may be employed for completing the operation as is found to be necessary or desirable, at least the final reamer being shaped and operated to produce the exact shape and size finally desired in the nose portion of the blank.

By these operations the interior size, shape and contour of the nose portion I34 is brought into accurate conformance with the predetermined standard desired in the finished and completed blank and corresponding to the size of the tip of the mandrel I46. The blank H2 is then replaced in the press apparatus illustrated in Fig. 16, omitting the collar I50 as illustrated in Fig. 19, in unheated condition, and then the mandrel I46 is again forced home in the blank I I2. With the ring I56 omitted the mandrel I46 may be forced completelyhome in the blank. The tip of the mandrel seats on the correspondingly formed interior of the nose portion of the blank and as it is thrust in, operates on the main body of the blank between the nose portion and the flange I66 which is held immovable by the block I42. This operation causes suflicient stretching of the blank in either a radial or axial direction, or both, to bring the entire interior surface of the blank into contact with the surface of the mandrel and so into the size, shape and form desired in the finished blank and as governed by the exterior size, shape and contour of the mandrel I46. Since the stretching is beyond the elastic limit of the metal the final form will be substantially .retained. It will, of course, be understood that this operation, like the operations illustrated in Fig. 16, is preferably accomplished while the surface of the mandrel I 46 is well lubricated as, for instance, with a mixture of white lead and graphite. Because of the irregular form of the original tube it maybe that parts of it will not need stretching to assume the size of the corresponding portion of the mandrel but the mandrel is forced into the blank with sufiicient pressure to stretch beyond the elastic limit the metal of those portions which are deformed with the result that after the mandrel is removed the interior of the blank remains substantially the size of the mandrel throughout its entire area. After this operation, the tube I I2 is preferably again subjected to a normalizing treatment and again pickled.

The blank thus produced is then inspected for the purpose of determining whether it will be capable, upon further operations, of producing a perfect completed blank. This inspection may involve the checking of all the external dimensions of the blank and rejecting all of such blanks as do not have enough metal on their exterior surfaces to properly clean up when the blank is externally machined to size. -Enough metal being assured on the exterior surfaces of the blank for such purposes, the interior surface of the blank is then thoroughly cleaned and visually inspected and all blanks having obvious defects internally thereof, such as holes, seams, folds or reamer marks making them unfit for use, are then rejected. In the absence of such defects the blank is then inspected to insure that its interior size, shape and contour sufficiently closely conform to the predetermined standard desired to I be acceptable for further operations. This is preferably accomplished by the use of another mandrel, such as I56 in Fig. 20, which is identical to the mandrel I46 in exterior size, shape and contour. The mandrel I56 is preferably first well lubricated as with white lead and/or graphite and is forced into the blank II2 under a pressure which, although not sufficient to permanently distort the blank, is sufficient to insure complete and accurate positioning of the mandrel therein. A suitable pressure will be adopted by one versed in the art. It may be desirable to employ in the neighborhood of two hundred tons for a blank of ordinary size. This having been done, it is then possible, by tapping the surface of the blank by suitable means such as a hammer I58, to determine if there are any areas of the blank which are not in full contact with the surface of the mandrel I56 and, if not in contact, the relative expanse of such area. If such area is present and the extent thereof too great to be acceptable, the area may be marked and then subjected to a swaging or other operation to reduce this par ticular portion of the blank and the blank again subject to the operation illustrated in Fig. 19 which will generally remedy the condition and. if remediedas determined by a repetition of the inspection steps above referred to, may then be carried on for further operations with other acceptable blanks. Each acceptable blank is then subjectedto the following operation.

It will be observed from an inspection of Fig. that the mandrel I56 is provided at opposite ends with center openings I60 and I62 respectively. The mandrel I56, with a blank I I2 mounted upon it, as indicated in Fig. 20, is then mounted in a lathe between centers such as I64 and I66 cooperating with the center openings I60 and I62 respectively. Conventional means such as the dog I68 may be employed for rotating the mandrel I56 and blank H2 in the lathe. Suitable means are employed for removing from the surface of the blank sufficient material to bring the wall to the desired thickness as measured from the surface of the internal mandrel. The lathe itself, as indicated in Figs. 21 and 22, may be modified for the purpose of this operation and some ofthese modifications are as follows. The usual cross feed on the lathe is disconnected and an air cylinder I10 is mounted on the back of the usual carriage I12. A piston I14 within the cylinder I10 is connected as by means of a piston rod I16 with the main transverse carriage slide I18. An air line I80 under suitable control is connected into the cylinder I10 between the piston I14 and the forward end thereof. A forwardly extending form member or template I82 is secured, as by means of screws I64 (see Fig. 22) to the forward face of the rear member of the bed of the lathe. A stud I88 fixed to and projecting downwardly from the under surface of the main cross slide I18 is provided at its lower end with a roller I90 in the plane of the form member or template I82. When air is introduced into the cylinder I10 through the hose connection I80, the pressure of the air acting upon the piston I14 urges the main cross slide I18 toward the rear and the roller I90 into contact with the forward surface of the template I82, and upon longitudinal movement of the carriage I12 of the lathe, the cross slide I18 and parts carried thereby are caused to move inwardly or outwardly in conformance with the configuration of the forward face of the template I82. In accordance with conventional construction, a compound slide I92 is carried by the main cross slide I18 and in turn is provided with a tool post I94 in which a suitable cutting tool, as for instance, a tool such as I96 may be secured.

The outer face of the template I82 is so formed that the roller I90 in moving across the face thereof will cause the point of the tool I96 to follow a path in exact accordance with the external shape desired in the finished blank, and the mandrel I56 is so located between the centers I64 and I66 as to bring the blank II2 axially into such position that it will transversely correspond with corresponding faces of the template I82. In this respect, it may be noted that the guiding edge of the template I82 is so formed and located with respect to the exterior surface of the mandrel I56, and consequently the inner surface of the blank II2, that the tool I96 in being guided by the template I82 in removing stock from the exterior surface of the blank II2 will cause the walls of the blank I I2 to taper from maximum thickness adjacent the shank I04 to minimum thickness at the outer end of the nose I34, the amount of taper thus provided varying according to that degree found desirable or necessary in the final product.

Accordingly, with the parts arranged as indicated and explained, the carriage I18 is run to one end of the lathe and the tool I96 is moved inwardly a sufiicient distance to take a roughing cut from the exterior of the blank II2. It is locked in this position and. then the longitudinal feed of the lathe is set so as to cause the tool I96 to travel over the length of the blank H2 in the path regulated by the template I82. 7 In this manner stock is removed from the exterior surface of the blank for instance fromthe extreme nose end thereof up to the flange I06, but no stock is removed from the flange I06 at this stage of the operation. If necessary, additional cuts are then taken from the exterior of the blank in the manner above described until the wall thickness of the blank approaches to within a few thousandths of an inch of that desired in the final product. At this point use of the tool I96 is discontinued. A suitable hand grinder (not shown) is then employed to remove material from the exterior of the blank so as to bring the blank to its exact final wall thickness and to impart a highly smooth finish to its exterior surface. If desired, the ground surface of the blank may then be additionally polished as by bufling or the like. The dimensions thus produced may approach exactness within as little as .002 of an inch.

When the above operation has been completed, the flange I06 is roughed out, preferably not closer than one-sixteenth of'an inch of finished size so as to leave ample material for finish and for use in connection with the balancing operations to be later described. This roughing out operation includes the step of breaking or beveling off the root end face of the flange I06, as at I98.

The next operation upon the blank deals with closing the nose of small end of the blank and this is preferably accomplished by the use of a spinning operation such as is indicated in Figs. 23 to 26, inclusive. In connection with the closing of the small end of the blank, it has been found desirable. although not necessary in all cases and particularly where the tip is relatively small, to increase the wall thickness of the blank at the extreme closed end portion thereof and also, although not necessary in all cases, to provide a projecting nipple about the point of closure for the reason that during pressing of the blank to blade shape a considerable amount of bending and stretching of the metal in the extreme (ill end portion occursiand unless a suitable amount of metal is provided at this point, particularly where the smallend of the blank is not relatively which accurately fits and is properly centered In carrying out this spinning operation the blank H2 being removed 'from the mandrel I56 is placed upon another mandrel, indicated at 200 in Figs. 23 to 26, inclusive. This mandrel formsthe subject of my application for'Letters Patent of the United States, Serial No. 718,573,

.filedApril 2, 1934, the same constituting a division of the present application. This mandrel 200 does not necessarilyneed to contact with the blank H2 over the full length of theblank but in any case must have an end portion 202' in the inner end portion of the nose 134 of the relieve itinpdiameter toward the tip. This relief, which is indicated at 202a, maybegin a engagement with the slide 2!!) 2 l 6 is preferably blank. Thefextreme'end of the portion" 202 is a rounded as at 204 into exact conformance with that desired for the interior surface of .theend of the blank. Preferably, the end surface 204 is partially spherical in shape with a center; 10-

After the mandrel 200 has been cated as at 206. thus formed it is preferable to cut it down or littleover an inch back from the tip and need not be very deep, as little as five thousandths of an inch havingbeen found satisfactory; The

purpose of this cut -is to keep the end .of 'the blank from actual contact with the mandrel.

It has been found that when the blank is in actual contact with the mandrel it is difllcult to keep the end of the blank hot enough to be conveniently and properly worked, By cutting out the mandrelas show'nthe blank is kept from contact therewith and the heat'is not so readily conducted -away from the portion of the blank which is to be spun.

The mandrel m with the blank H2 thereon is then mounted in a suitable lathe or other turnmay include, as indicated in I ing machine which Fig. 24, a bed 208 upon'which islongitudinally' movable a main slide ported a compound slide H2. The nose end of the blank may be suitably supported as by a steady rest 2l4,"care being taken in adjusting it any subsequent expansion of the to allow for blank which may-occur due to heating the tip .thereof for the spinning operation. A stop 216,

as indicated in Fig. 24, is preferably provided for movement of. the carriage 2H) and consequently the pivotal axis 2") of to the left as viewed in the figure.

adjusted and fixed so that the pivotal center 2l8 ofthe compound carriage 212, and consequently the spinning'tool 220 carried thereby, may be limited in its approach toward the center 206v of the end surface 204 of the mandrel by a distance indicated in Fig. 23 at 222 equal to the added wall thickness desired for the extreme tip portion of the blank H2.

In operation, and referring now to Fig. 24,

the mandrel 200 and blank H2 are rotated in 7 small, a crack is liable to develop in the finished article.

2lll upon whichis supso as to limit' thecompound slide 2l2 The stop the spinning tool 220 is thus brought to a position such that when itis swung about the axis 2l8 it will engage only the extreme end portion of the nose I34 of'theblank' H2. As soon as the heat from the flame of the torch 224 has brought the extreme end-portion of the blank to .a suflicient condition of plasticity, as above described, the compound carriage H2 and the tool 220' carried thereby is swung about the axis 2l-8, preferably in a counter-clockwise direction as 1 viewed in Fig. 24, and the tool 220 thus coming in contact with the extreme end portion of the nose or tip causes it to be spun in as indicated in,Fig. 24. The main slide 2|0 is then moved a short distance to the left, as'viewed in the figj urea-until the distance 226*in Fig. 24 has been reduced, for instance, to a distance indicated at 228 in Fig. 25.at which time the tool 220 is again swunguaround the pivotal axis 2I8 to spin the extreme tip of the blade further inwardly as in- "1 dicated in Fig. 25. This movement of .the main slide 2) carrying with. it the spinning tool 220 is repeated .as many times as 'is desirable or necessary, taking care that each pass of the tool 220 is an easy pass so as to insure a smooth flow of the metal of the tip, and until the carriage 2) has finally been brought up against the stop 2l6 and the tool 220 has caused the outer surface of the extreme tip of the blank to be spun into a semi-spherical surface merging smoothly with the outer 'wall of the nose I34 of the'blank H2 as indicated in Fig. 26. Toward the end of the operation one of the passes of the tool 220 will go past the center of the blank thus ensuring as complete a closure of the end as possible. An excess of metal is provided in the endof the blank so that the tip wall may be somewhat thicker than the immediately adjoining part. After the tip'has been closed the last pass of thetool 220 is restrained from passing center and so manipulated as to raise at the extreme end of. the blank a small nipple 230 as clearly indicated in Fig. 26. It is understood, of course, thatthe flame from the torch 224 continues to play against the tip end of the blank during these operations and may keep such end at such temperature that when the end is finally closed as indicated'in Fig. 26, themetal of the tip may weld itself together at the line or point of closure.

The thickened end portion surmounted by the nipple 230 reinforces the end of the blank 50 thatit may not break open under the stresses produced when the blank is deformed into the blade form in the pressing dies to be described. Upon completion of the closing operations on the end of" the blank the newly closed end por- -tion or the blank is preferably polished and buffed so as to bring it to the same condition of finish as the main body portion of the blank.

- The next operation is to normalize-the newly formed tip portion of the blade to restore its proper grain structure and this step may be conveniently accomplished by heating the tip end of the blank to about 1625 F. to 1675 F., in case of the particular metal specified, and allowing it to slowly cool in a sand box to below 1200 F. In order to avoid surface disturbance during this operation, the'blank may be coated with some such protective material as Kemick. After the tip has been normalized in this manner thelength of theblank is then checked and any blank whose length is obviously too great or too small to be acceptable in the final product is rejected;

in the device shown in Figs; 44, 45 and 46 to determine whether or not it will be possible to form the finished'flange I06 out of. the material I provided therefor in the blank as thus far formed,

and still maintain the proper moment in the finished blade as measured from the tip face of the finished flange I06. The method of determining this fact with the apparatus indicated in Figs. 44, 45 and .46 will be fully apparent in the description which will follow later in regard to locating the tip face of the flange I06 with respect to the center of mass of the blade, and consequently a' detailed description of this apparatus and the manner of employing it to deter mine the question of sufliciency of stock in the' rough flange I06 will not be. given at this point.

It may be mentioned, however, that should such W apparatus indicate that there is not sumcient stock in the rough flange M6 for this purpose, andit is not -possible to bufi down the outer surface ofthe blank so as to sufficiently shift the center of gravity of .the blank to remedy this de feet, as is possible in some cases, then the blank is rejected. V

The next operation is to determine whether or not the blank is heavier on one side or the other and, if so, to mark the heavy side. If necessary,

the blank may be straightened before proceeding. Whether or not the blank has a heavy side is determined by mounting it upon a pair of horizontal spaced parallel knife edges 232, as indicated in Figs. 27 and 28, the heavier side, if any, of course comingto rest at the bottomof the blank on the knife blades, and the flange W6 is then marked to indicate the heavy side for reasons which will hereinafter be apparent; In

cases where such blanks are in quantity production, it is also preferable at this point to stamp the serial number and the blank number on the outside diameter of the flange I06 so as to enable later identification.

After the above operation the blank is then weighed again to again check its accuracy and to insure that it comes within the permissible limits ofweights necessary to produce satisfactory final blades, and if found to be satisfactory, it is then subjected to a suitable treatment to remove all rust, grease or other foreign matter from both inner and outer surfaces. This cleaning operation may be accomplished, as a matter of illustration, by the use of a product commercially known as Deoxidine and placed on the market by the American Chemical Paint Company, of Ambler, Pennsylvania. After the blank has thus been thoroughly cleaned, it is coated inside and outside with a material designed to keep its surface clean and to prevent oxidization and decarburization of its surface under the influence of heat, and .then placed in a furnace. Such coating material may, for instance, be coal oil but I prefer to employ a material particularly prepared for such purpose and commercially produced and marketed under the name of Kemick by the American Chemical Paint Com pany, of Ambler, Pennsylvania, and which is more-or-less in the nature of a paint and is similarly applied. The blank, especially when so protected, may be heated in any suitable type of furnace, heated in any suitable or conventional manner and capable of simultaneously receiv,

ing one or more blades therein, for further manipulation.

One suitable type of such furnace is indicated in Fig. 29 by way of illustration only. As indi- 5, 1933, Serial No. 679,134. It

The acceptable blanks are then placed singly cated in this figure, the furnace is shown as having refractory walls 234 and a central opening 236 in the top thereof in which is received and supported a suitably sized tube 238 closed at its bottom. and open at 'its top. Brackets 240 are secured to the inner surface of the tube 238 a suitable distance downwardly from the top thereof, and by means of these brackets the blank H2 may be suspended vertically by inter-engagement of its flange I96 therewith, in generally spaced relation with respect to the sides of the tube 238 and in such a position that there is no possibility of setting up stresses -in the walls of the blank which might cause distortion of the blank so that it would not properly align with the die depressions in the operations hereinafter described. A

cover member 242 is preferably placed over the upper end of the tube 238 during the heating process so as to prevent possible circulation of air in the tube 238 and blank H2. A suitable flame may be introduced into the furnace 234. as by means of a tube 244 which projects through the walls of the furnace adjacent the bottom thereof and the products of combustion may be exhausted from the furnace as through' a tube such as 246 positioned adjacent the top of the furnace, so asto insure an even heating of, the tube 238 and the blank 2 contained therein. The blank H2 is allowed toremain in the furnace for a sufiicient length of time tobring its temperature up to that suitable for forming, ap-

- proximately 1625 to 1675 F. in' the case of the be, for instance,fifteen to twenty minutes, it is then removed and immediately placed in the dies which are provided for pressing the blank to blade shape, and which, as will later be described,

may be further employed for the purpose of quenching the blade. I

An understanding of the, methodfollowed in 'pressing'the blank to blade shape in the dies will, however, be of aid in the proper understanding of the die structure and, accordingly, a short statement of this method is given at this point.

The dies themselves form no part of the present invention but constitute the subject matter of my co-pending application for Letters Patent of the ignited States for improvenients'in Apparatus or forming propeller blades, filed July will be understood that the die structure includes two main parts relatively movable toward and away from each other, the adjacent faces of the parts having opposed depressions therein which cooperate,

when the dies are in. closed position, to form a recess of the exact shape and contour and, ex-

cept preferably for the-outer stages of the blade,

as will be explained in greater detail, the exact size of the desired finished blade. In this connection it may be noted thatin the broader aspects of the presentinvention'thedie depressions may cooperate to form adepression conforming exactly. throughout to the exact size, shape and contour of the desired finished blade, but a more limited phase of my invention deals with making the outer or tip stages of the depressions wider and longer than the corresponding portions of the desired blade, this having been found desirable under certain conditions, and accordingly this last feature is shown in the drawings,- the former being apparent therefrom.

2,081,645 p I I forming a large number of highly heated blanks In operation, the blank is taken from a furnace such as that described in connection with Fig. 29 for instance, in a highly heated condition, the die parts are $1 ead apart, the heated blank is placed between the die parts and its interior is placed under a suitable air pressure, and the dies are then brought "together, causing the exterior of the blank to assume the shape of the walls of the die depressions. The purpose of placing the interior of the blank under air pressure is to cause it to be expansively pressed outwardly into contact with the walls of the die.

depressions during the pressing operation, thereby insuring substantially complete contact between the blank and the walls of the depressions over the entire outer surface of the blank. air pressure employed for, this purpose, while high enough to insure the eifectiveness of its purpose is, of course, not sufilciently high to endanger bursting of the walls of the blank. It has been found that an air pressure of three hundred pounds per square inch is usually ample for the purpose described, but this pressure may vary in accordance with the size and wall thickness of the particular blank being worked upon. In applying such air pressure to the interior of the blank it is, of course, necessary for optimum results that such pressure be exerted at the desired maximumvalue substantially immediately upon admitting the air to the blank and be maintained at such value during the operation; For this reason it is preferable to employ an air reservoir tank (not shown) in connection with the air supply and maintain the pressure in it at a sufiiciently hig figure to insure an ample supply of air for the ope ation at the desired value. An air pressure of 300 pounds per squareinch is preferably employed in the blank during the pressing operation.

In any case it will be apparent in connection with this phase of operation that the temperature of'the blank and the pressure of the air to which the interior of the blank is subjected have, of course, a certain relation between them, the temperature necessarily being such as to permit the necessary bending of the walls of the blank into blade formation without causing any undesirable stress or fracture of the metal of the walls and, of course, suinciently high to insure the internal pressure of the air forcing the blank into substantial contact with all surfaces of the die depressions when the dies are brought together, but preferably a temperature not so high as to permit the expansive force of the air to stretch the metal of the blank.

In placing the heated blank between the dies, it is further desirable to maintain the main body portion of the blank out of contact with the dies until the dies are actually brought together, for otherwise any area of the blank which contacted with the dies might be cooled to such an extent that when the dies were brought together that area would have become so rigid as not to properly conform to the shape of the corresponding depression wall area of the dies. Unequal cooling might also set up undesirable unequal. stresses in the metal at various points in the blank. In view of the fact that the shank portion I64 of the blank is not deformed during the pressing operation, this portion of the blank is preferably employed for supporting the blank in "the dies before the dies are brought together as it thusmakes little difference whether it is pre-cooled or not.

Where the dies are employed for successively The,

to blade shape, by repeated contact with successive heated blanks the die parts in some cases are liable to be heated to such a degree as to become detrimental, and for this reason it may be preferable to provide suitable means for regulating thetemperature of the die parts. This may conveniently be accomplished by circulating a controlled supply of water through the die parts. Furthermore, in view of-the fact that a preferred later step in the manufacture of the blades is a quenching operation to harden the blade material, and a preferred method of quenching the blades is to place them between relatively cold die parts contacting substantially the entire outer surface of the blades, the same die parts as are employed for forming the blanks to blade shape may be employed in quantity production for the quenching operation if suitable means are provided for cooling the die parts. The water passages referred to above ofier a suitable means for accomplishing the desired cooling of the die parts.

In the form shown in Figs. 30 to 37, inclusive, .my improved propeller blade forming apparatus includes a lower block or die holder 256 which normally rests upon the lowerplaten of a press, and is provided with a longitudinal recess 252 which i bounded by a vertical side wall 254 and an nclined side wall 256. As indicated in Fig. 32, the die holder 250 iscored internally or otherwise suitably provided with passages 258 ,for circulating a cooling medium substantially thereon. The opposite front corner portions of the upper die'holder are provided with recesses .210 for slidably receiving the'posts 264' of the lower die holder. The side wall 212 of the recess 26B is vertical and is located substantially in alignment with, the side wall 254 of the lower recess 252, and the other side wall 214 of the recess 268 is'inclined oppositely with respect to the side wall 256 of the other recess.

Seated in the recesses 252 and 268 of the die I holders 2,50 and 266 are dies 216 and 211 respectively having longitudinally extending blade forming recesses 218 and 219 respectively formed in their opposed faces which recesses cooperate to form a single recess which conforms in size, shape, contour and pitch with the size, shape and contour, except forthe nose end as will hereinafter be more fully explained, and pitch of the finished blade shown in Fig. 1 which it is desired to form. The die parts 216 and 211 are preferably split transversely of their length and intermediate their ends as at 280 and are de' tachably secured to their respective die holders by longitudinally extending gibs or wedge members 284 and 286 (see Fig. 35) which are held in place by bolts 288 and 290 respectively screwed into the die holders 256 and 266 respectively. The dies are held against outward or lateral displacement from the recesses bythe inclined walls thereof and by the inclined sides of the gibs 28 i and 286.

By replacing those portions of the dies 216 and 211 inwardly of the line of split by portions of either greater or lesser length than those shown, the same outer die portions may be employed to produce blades of different lengths. By this means a considerable saving in die costs may be realized in the production of blades of different lengths. It may be desired to employ various butt end die sections with varying tip end die sections and the construction described makes them easily interchangeable to produce any desired combination, without the necessity of making complete dies of all the various types needed.

It will also be noted from an inspection of Figs. 31, 32 and that the depressions 218 and 219 in the dies 216 and 211 are wider and longer than the corresponding portion of the blade in the outer stages thereof. This may exist for as much as sixty percent of the length of the blade toward the tip end. This is arranged by extending those surfaces of the die depressions 218 and 219 which give such portion of the blade its desired surface conformation in length, out to near the parting line of the dies, and extending the corresponding surfaces of the dies laterally to near the parting line in a tangential direction w th respect to the natural radius of the respective edge portions of the blades formed therein. This permits the making of blades of various .lengths with the pitch twist continuing uniformly together with the proper longitudinal and lateral conformation.

It is to be understood that except for the outer portions of the depressions 218 and 219 which may be made wider and longer than the corresponding portions of the blades to be produced thereby, as above pointed out, the perimetrical dimensions of the d e depressions at any given transverse cross section through them is substantially equal to the perimetrical dimensions of the corresponding section of the blank M2 to be shaped between them, so that when the blank is pressed to blade shape, no outward stretching or inward crowd ng of the metal of the blank occurs, such metal being merely bent to shape.

The upper die holder 266 is internally cored or otherwise suitably provided with cooling mediurn passages 292 which communicate with a supply p pe 2% and a drain pipe 296 at the opposite sides-of the holder.

A pair of parallel plates 298 are located adjacent the outer sides of the upright posts 26% of the lower die holder and are rigidly secured thereto by bolts30li. The plates 298 protrude beyond the forward ends of the die holders and they are provided at their outer extremities with inwardly extending cleats 302 which are secured in placeby bolts 304. The cleats 302 form channel ways 306 between their inner sides and the front edges of the posts 25 in which'side flanges 308 and sac of a channel shaped support or cross head 2H2, having a web 314, are slidably received. As best shown in Figs. 31 and 37, the inner edge portions ofthe flanges 308 and 3? are provided with recesses 3H5 in which shoes 3H3. preferably comprising rectangular metal bars, are seated. The shoes 3E8 carry pins 320 which are received in apertures 322 formed in the posts 2% of the lower die holder 250 and the shoes are yieldably held in spaced relation to the posts 23% by springs 32 5 which surround the pins 320 and are seated in recesses 326 in the forward edges of the posts and surrounding the apertures 322. These shoes"3l8 normally bear upon the cross head 3l2 urging the same outwardly against the inner sides of the cleats 302.

As best shown in Fig. 36, the entire cross head M2 is yieldably supported on coil springs 328 which are seated upon the lower press platen 330. The springs 328 normally hold the cross head 312, and the blank H2 when supported thereby, more or less centered between the dies and out of contact with both dies, as indicated in Fig. 36.

The web 3M of the cross head 3l2 is provided with an enlarged central opening 330 of circular contour in which a collar 332 for receiving the shank portion I04 of the tubular blank H2 is detachably mounted by screws 334. The collar 332 is provided with preferably horizontally and laterally extending slots 336 which may register with the flattened portions toward the leading and trailing edges which are formed on the resulting blade and permit the blade to be withdrawn from and through the collar during removal of the blade from the forging apparatus. I

The forming apparatus may be readily conditioned for manufacturing blades of various dimensions by removing the collar 332 and replacing it with a collar of suitable inner diameter and by substituting proper dies or die sections for the dies 216 and 211 shown; The cross head 3l2 serves as the sole support for the propeller blade blank before the dies are brought together and by reason of the elevated position in which it is held by the springs 328, it locates the tubular blank H2 in spaced relation between the dies 216 and 211 when they are spread apart and in registration with their recesses 218 and 219 and holds the blank out of contact with the dies and their supporting structures so as to prevent cooling of localized areas of the blank before compression thereof to blade shape.

In supporting the blank internally by pneumatic or other fluid pressure after it is positioned in the collar 332, it is necessary to form a communicative connection between the open end of the blank and a source of pressure in a brief time interval in order to prevent excessive cooling of the blank before the forming operation. This is successfully accomplished by providing the connecting means on a breech block 338 which is swingably gnounted on a vertical breech block pin 5% that is mounted in brackets 342 on the flange 3H9 of the cross head 3i2. A relatively positive seating of the air inlet 356 on the flange its should be provided. This may be accomplished by a suitable washer or other contacting member, or the contacting member may be soniewhat resilient. Such a resilient seating device' is illustrated as provided by the sylphon or bellows 3 but this may not be essential. inner side of the breech block 338 has a recess 3st in which the outer end of a metallic bellows or sylphon 3 36 is suitably secured in sealed relation therewith. Mounted on the inner end of the bellows or sylphon 346 is a head 348 having a central protruding boss which is received in the open end of the tubular blank 5 HE. A washer or gasket 358, preferably comprising copper or other suitable material, is provided between the flange tee-of the root end of the tubular blank and the face of the head 388 for forming an air tight seal between the head of the bellows and the flange of the blank.

The)

Leading to the interior of. the bellows 346 and formed in the breech block 338 is an aperture 352 in which a nipple of an outwardly extending valve 354 is mounted- The valve 354 communicates through a flexible connection with a source of pressure (not shown) and when open supplies air or other gas under pressure to the interior of the bellows 346 and from the latter to the interior of the tubular blank through a restricted orifice 358 in the head 348 of the bellows. The side of the head 348 within the bellows 346 is larger in area than the end of the boss which extends into the open extremity of the blank and therefore a force differential is created by the pressure on theopposite sides of the head 348 which presses the gasket 350 upon the flange I06 of the blank with a pressure of large magnitude, thus forming an effective seal at the open end of the blank. Any leakage which may occur from the interior of the blank tends to increase this force 'diflerential and accordingly increases the pressure upon the extremity of the blank preventing continuedleakage. In practice, with the pressure of 300 pounds per square inch in the blank. a load of 6000 pounds may be exerted on the flange by suitably proportioning the parts referred to, thus tending to insure sufllcient pressure within the blank to cause it to hug the dies when they are closed.

As best shown in Figs. 30 and 31, the breech block is releasably held in a closed position by a latch device which includes a vertical cylindrical bar 358 journaled in bearings 360 mounted on the flange 308 of the cross head 3I2. This bar is provided with an axially extending V-shaped groove in its surface and it is provided with an outwardly extend ng radial pin 362 by which it may be rotated to bring the V-shaped groove into registration with a protruding edge portion 364 on the free side of the breech block. Adiacent the projecting lip 364 of the breech block is a recess 385 in which the cylindrical portion of the bar 358 is received when the latter is held in looking position by the spring 368 engaging the pin 362. The breech block may be unlocked and swung to open position, shown in dotted lines in Fig. 31. by moving the pin 382' against the tension of the spring 368 and so rotating the bar 358 in a counter clockwise direction to allow the rojecting lip 364 on the breech block to pass by the groove in the bar 358.

In operation, either the upper or lower die holders may be moved so as to bring the dies together, but the lower die holder 250 is preferably lifted vertically upward with substantial iorce by mechanism (not shown) of the character customarily used in die forming operations. A tubular blank II2 of the type shown in Fig. 2'1, having a flange I06 on its openend is heated to a workable temperature as in the manner described in connection with Fig. 29 and is lifted preferably by tongs inserted in the open end of the blank and inserted through the central opening in the replaceable collar 332 while the cross head 3I2, lower die holder 250 and upper die holder 2.66 are'in the relative positions shown in Fig. 36, and while the breech block 330 is open. In order to obtain uniformity of final product and insure optimum conditions of balance in the finished product, the heavy side of the blank, if any, as determined. and marked in the manner described in connection with Figs. 27 and 28, is positioned on the centerline of the dies which form the flat face Ilb of the blade, these being the lower dies 216 and 218, as shown. The blank H2 is' inserted through the central opening of the collar 332 until the flange I06 thereof engages the outer side of the collar and then the breech block 338 is swung to a closed position with the tions the blank in registration with the recesses 218 and219 of the dies 216 and 211, and holds the blank out of contact with the dies and their supporting structureso as to prevent pre-cooling of localized areas of the blade, as previously mentioned, although it may be that; at least'before the breech block is shut, the blade being more or less loosely held in collar 332, may sag so as to touch the die at its tip, but this may not be harmful as the nipple .230 or thethicker wall may prevent dangerous pre-cooling during the short period of contact if any.

Before the lower die holder 250 and die 216 are urged upwardly to compress the blank to blade shape, the valve 354 is opened so as to admit air into the bellows 346 and to supply air to the interior of the tubular blank. The pressure in the interior of the bellows is applied directly on theinner side of the head 348, holding the head in air sealing relation against the flange I06 of the blank. A pressure of 300 pounds per square inch is preferably employed where a. blank of usual size is made of the ordinary range of low carbon steels and this pressure is preferably substantially immediately built up in the blank so as to internally support the latter and to hold all portions of its wall in contact with the surfaces of the recesses in the dies when the lower die is urged upwardly from the position shown in Fig. 36. The lower die, in moving upwardly, first engages the blank and rapidly moves it, together with the cross head 3l2, upwardly against the weight of the blank. and the force of the springs 328 until the dies 216 and 211 contact with each other and the blank which then assumes its desired blade shape inthe depressions 218 and 218 between them. The flanged end of the blank, of course, constantly maintains its engagement with the head 348 during movement of the cross head in the die closing operation. The closing movement of the dies is so rapid that the dies contact the entire blank at as near the same time as possible. This is desirable in order to avoid unequal chilling which'might occur if there was die contact at one point before another. This rapid and -complete'fcontact makes it possible to act upon the blank while all the metal is at a temperature to be readily shaped.

As the blank cools and shrinks its tapered end is free to contract longitudinally in the tapered portions of the die recesses. The other end portion of the blank, however, is allowed to move inwardly with respect to the dies against the action of the springs 324 which yieldably hold the cross head 3I2, upon which the flange I06 of the blank -I I2 bears, in spaced relation to, the adjacent ends of the die holders. In this manner, setting up of internal strains in the propeller blade during cooling thereof is minimized.

The dies and die holders may be protected from overheating by repeated contact with successive blanks, when used continuously in such pressing operations, by circuating a cooling medium through the passages 258 in the lower die holder and 232 in the upper dieholder. As previously mentioned, the provision of such cooling medium 

